Positive photoresist composition and resist pattern formation

ABSTRACT

A means for increasing development velocity of a positive photoresist composition is provided which contains a photosensitive novolak resin formed by replacing some hydrogen atoms within those of all phenolic hydroxyl groups of alkali soluble novolak resin by 1,2-naphthoquinonediazide sulfonyl group. This means is positive photoresist composition and a formation method of a resist pattern using the composition which contains (A) a photosensitive novolak resin formed by replacing some hydrogen atoms within those of all phenolic hydroxyl groups of alkali soluble novolak resin by 1,2-naphthoquinonediazide sulfonyl group, which is dissolved in (B) propylene glycol alkyl ether acetate.

TECHNICAL FIELD

The present invention relates to a positive photoresist composition andto a resist pattern formation method.

Priority is claimed on Japanese Patent Application No. 2003-325953,filed Sep. 18, 2003, the content of which is incorporated herein byreference.

BACKGROUND ART

In photolithography technology, the positive photoresist compositionwhich mainly contains an alkali soluble resin and a quinonediazide groupcontaining compound as a photosensitizer is conventionally used formanufacture of a semiconductor device or a liquid crystal element. Thispositive photoresist composition has the characteristics of being ableto be equal to practical use, in the manufacture of a semiconductordevice or a liquid crystal element. However, in the steps in amanufacture field which requires thick film process, such as, forexample, the bump formation process of an LCD driver etc., the maximumwiring process of CSP (Chip Size/Scale Package), the process which formsthe magnetic coil of a magnetic head, it is required to form a resistpattern with sufficient perpendicularity, at a high sensitivity and witha high development velocity under, for example, thick film conditions of3 μm or more. However, it is difficult to satisfy the requirement undersuch thick film conditions using the conventional positive photoresistcomposition.

On the other hand, positive photoresist compositions which comprisephotosensitive novolak resin formed from an alkali soluble novolak resinwherein some hydrogen atoms within those of all phenolic hydroxyl groupsof the resin are substituted by 1,2-naphthoquinone diazide sulfonylgroups are described as a material suitable for the exposure processunder thick film conditions in patent documents 1-4.

[Patent document 1] Japanese Unexamined Patent Application, FirstPublication No. 2001-312052

[Patent document 2] Japanese Unexamined Patent Application, FirstPublication No. 2001-312059

[Patent document 3] Japanese Unexamined Patent Application, FirstPublication No. 2001-312060

[Patent document 4] Japanese Unexamined Patent Application, FirstPublication No. 2001-312066

However, according to research of the present inventors, although thepositive photoresist composition comprising a photosensitive novolakresin formed from an alkali soluble novolak resin wherein some hydrogenatoms within those of all phenolic hydroxyl groups of the alkali solublenovolak resin is substituted by 1,2-naphthoquinone diazide sulfonylgroup is suitable for realizing the perpendicularity and highsensitivity of a resist pattern in a thick film, the composition has aproblem that development velocity thereof is slow.

DISCLOSURE OF THE INVENTION

Therefore, an object of the present invention is to increase thedevelopment velocity of the positive photoresist composition comprisinga photosensitive novolak resin formed from an alkali soluble novolakresin wherein some hydrogen atoms within those of all phenolic hydroxylgroups of the alkali soluble novolak resin are substituted by1,2-naphthoquinone diazide sulfonyl group.

In order to attain the above-mentioned purpose, the present inventionadopts the following features.

The first aspect of the present invention is a positive photoresistcomposition formed by dissolving (A) photosensitive novolak resincomprising an alkali soluble novolak resin wherein some hydrogen atomswithin those of all phenolic hydroxyl groups of the alkali solublenovolak resin are substituted by 1,2-naphthoquinone diazide sulfonylgroups, in (B) an organic solvent containing propylene glycol alkylether acetate.

The second aspect of the present invention is a resist pattern formationmethod comprising the steps of coating a positive photoresistcomposition of the present invention on a substrate, prebaking thecoated film, selectively exposing the film, and subsequently alkalideveloping the film.

EFFECTS OF THE INVENTION

According to the present invention, the development velocity of thepositive photoresist composition comprising a photosensitive novolakresin formed from an alkali soluble novolak resin wherein some hydrogenatoms within those of all phenolic hydroxyl groups of the alkali solublenovolak resin are substituted by 1,2-naphthoquinone diazide sulfonylgroup can be inceased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the measuring method of an Example.

BEST MODE FOR CARRYING OUT THE INVENTION

[Positive Photoresist Composition]

(A) Component (Photosensitive Novolak Resin)

The component (A) is a photosensitive novolak resin formed from analkali soluble novolak resin wherein some hydrogen atoms within those ofall phenolic hydroxyl groups of the alkali soluble novolak resin aresubstituted by 1,2-naphthoquinonediazide sulfonyl group.

By using the component (A) the perpendicularity of the form of a resistpattern and a good sensitivity are obtained.

The component (A) can be synthesized through an esterification reactionof an alkali soluble novolak resin and a 1,2-naphthoquinone diazidesulfonic acid compound. The alkali soluble novolak resin can besynthesized as a polycondensation material through the dehydrationcondensation reaction of a phenolic compound and a condensing agentaccording to a usual method, such as is disclosed in Japanese UnexaminedPatent Application, First Publication No. 10-97066, for example.

-1,2-naphthoquinone diazide Sulfonic Acid Compound

Examples of the above 1,2-naphthoquinone diazide sulfonic acid compoundincludes, e.g., halide of quinone diazide compounds, such as1,2-naphthoquinone diazide-4-sulfonic acid chloride, 1,2-naphthoquinonediazide-5-sulfonic acid chloride.

-Alkali Soluble Novolak Resin

As examples of the above phenolic compound which may be used forsynthesis of an alkali soluble novolak resin, the phenolic compoundcorresponding to the constitutional unit represented by the followingformulas (a-1) to (a-5) can be mentioned.

For example, as a phenolic compound corresponding to the constitutionalunit represented by the above formula (a-1), m-cresol can be mentioned;

as a phenolic compound corresponding to the constitutional unitrepresented by the above formula (a-2), p-cresol can be mentioned;

as a phenolic compound corresponding to the constitutional unitrepresented by the above formula (a-3), 3,4-xylenol can be mentioned;

as a phenolic compound corresponding to the constitutional unitrepresented by the above formula (a-4), 2,3,5-trimethylphenol can bementioned; and

as a phenolic compound corresponding to the above formula (a-5),3,5-xylenol can be mentioned.

Moreover, although phenolic compounds other than the above can also beused, as for these, it is desirable to use such phenolic compounds in anamount not more than 10 mol % based on all phenolic compounds from theviewpoint of not spoiling various characteristics of the positivephotoresist composition of the present invention.

As the above condensing agent, aldehydes and ketones conventionally usedfor synthesis of phenol novolak resin can be mentioned, and aldehydes,especially formaldehyde is particularly preferable.

Alkali soluble novolak resins satisfying the following characteristicsshown below at items (1) to (3) are desirable.

(1) the polystyrene equivalent weight average molecular weight of1000-30000, preferably 2000-10000, (2) degree of distribution of 25 orless, preferably ten or less, and (3) the dissolution rate to a 2.38% byweight TMAH (tetramethyl ammonium hydroxide) aqueous solution (23° C.)of 10 to 1000 Å/s, preferably 50 to 500 Å/s.

When the weight average molecular weight is 1000 or more, as shown inthe above (1), thickness loss of the non-exposed part at the time ofdevelopment can be controlled, and when the weight average molecularweight is 30000 or less, the fall of development velocity andresolvability can be controlled.

When the degree of dispersion is 25 or less as shown in above (2), it isadvantageous in acquiring resolvability and good form.

When the dissolution rate is 10 Å/s or more, thickness loss of thenon-exposed part at the time of development can be controlled, and thefall of development velocity can be controlled by being 1000 Å/s orless.

Here, the value of the dissolution rate of alkali soluble novolak resinin this specification is a value specifically calculated as follows.First, on a silicone wafer, a solution (concentration: 22% by weight)formed by dissolving an alkali soluble novolak resin in propylene glycolmethyl ether acetate is applied, the resulting coating is prebaked for90 seconds at 110° C., and the resin film of 1000 Å thickness is formed.Next, this wafer is dipped in a 2.38% by weight TMAH developer at 23° C.The time for the resin film to dissolve completely is measured and theamount of thickness loss of the resin film per unit time (Å/s) iscalculated therefrom.

The thus obtained amount of thickness losses of the resin film per unittime is the dissolution rate of alkali soluble novolak resin in thisspecification.

-(A) Component (Photosensitive Novolak Resin)

The polystyrene equivalent weight average molecular weight (Mw) obtainedby a Gel Permeation Chromatography (GPC) of an alkali soluble novolakresin of the (A) component before substitution by 1,2-naphthoquinonediazide sulfonyl group, is preferably 1000-30000, and more preferably2000-10,000. By making the Mw 1000 or more, a tendency can be controlledof a remarkable thickness loss of a non-exposed part and a difficulty information of a resist pattern at the time when the development takeplace. Moreover, by making the Mw 30000 or less, a tendency fordevelopment velocity and resolvability to decrease remarkably can becontrolled.

Moreover, the alkali soluble novolak resin of (A) component beforesubstitution by 1,2-naphthoquinone diazide sulfonyl group can, ifnecessary, be decreased in low molecular weight components content, byfractionation processing not more than in 80% by weight, more preferablynot more than 50% by weight before this fractionation processing.

Here, the low molecular weight component means the above phenoliccompound, i.e., phenolic monomer, the dimer obtained from the phenoliccompound, the dimer obtained from the phenolic monomer of the phenoliccompound, and the trimmer obtained from phenolic monomer and the like.

By using such fractionated resin, the perpendicularity of the resistpattern sectional form becomes still better, the generation of aresidual substance (scums) on the substrate after development decreases,and resolvability improves. Moreover, the resist becomes excelled inheat resistance.

The fractionation processing can be performed by a well-knownfractionation processing method, for example, by the followingfractional precipitation processings. First, as mentioned above, afterperforming the dehydration condensation reaction of a phenolic compoundand a condensing agent, the obtained polycondensation product (novolakresin) is dissolved in a polar solvent, and poor solvents, such aswater, heptane, hexane, pentane, and cyclohexane, or the like is addedto the resulting solution. Since low molecular weight components havecomparatively high solubility and they are dissolved in the poor solventat this time, the fractionated resin with which the content of lowmolecular weight components are reduced can be obtained by filtratingdeposited materials.

Examples of the above polar solvent are alcohols, such as methanol andethanol; ketones, such as acetone, and methyl ethyl ketone; glycol etheresters, such as ethylene glycol monoethyl ether acetate; and cyclicethers, such as tetrahydrofuran, etc.

The content of low molecular weight components in alkali soluble novolakresin of the (A) component before substitution by 1,2-naphthoquinonediazide sulfonyl group can be checked from the result of GPCmeasurement. That is, from a GPC chart, the molecular weightdistribution of the synthesized phenol novolak resin can be checked, andthe content can be calculated by measuring the intensity ratio of thepeak corresponding to the elution time of low molecular weightcomponents.

In addition, since the elution time of the low molecular weightcomponent changes with measurement means, specification of a column, aneluate, a flow rate, temperature, a detecting element, sampleconcentration, an injection rate, a measuring instrument, etc., isimportant for it. In the present invention, by using the followingmeasurement means, the elution time of a phenolic monomer can beassigned to around 23 to 25 minutes, the elution time of a dimer can beassigned to around 22 minutes, and a trimer's elution time can beassigned to around 21 minutes, respectively.

(Measurement Means of GPC in the Present Invention)

(1) 20 mg of a sample is dissolved in 10 ml of tetrahydrofuran (THF),and a sample solution is prepared.

(2) 10 microliters of sample solutions of (1) is poured into followingGPC measurement equipment and is flowed for 28 minutes, and the elutiontime of the sample detected near UV wavelength λ=280 nm is measured.

(Measurement Equipment)

GPC measurement equippment (trade name: “GPC SYSTEM 11”; manufactured byShodex) provided with a guard column (trade name: “KF-G”; manufacturedby Shodex), and three separation columns (trade name: “KF-801”;manufactured by Shodex; column size 8 μm (diameter)×300 mm (length);packed with styrene-divinylbenzene copolymer of 6 μm grain size;), theseparation column temperature being set at 40° C.

Elution liquid passing velocity of the eluate tetrahydrofuran (THF) isperformed on condition of 1.0 ml/min.

The degree of dispersion [Mw/number average molecular weight (Mn)] offractionation resin is preferably 3.0 or less, and more preferably 2.2to 2.8. By making Mw/Mn 3.0 or less, the resolvability, theperpendicularity of a resist pattern, and the heat resistance of thepositive photoresist composition of the present invention improve.

The alkali soluble novolak resin component of the (A) component beforesubstitution by 1,2-naphthoquinone diazide sulfonyl group comprises,within all phenolic constitutional units, a combination of theconstitutional unit of the above formula (a-1), and at least oneconstitutional unit selected from the above formula (a-2), (a-3), (a-4)and (a-5) in respect of developability, resolvability, and form.

The rate of the hydrogen atoms which is substituted by1,2-naphthoquinonediazide sulfonyl group within the hydrogen atoms ofall phenolic hydroxyl groups of alkali soluble novolak resin in the (A)component, i.e., the reaction rate of an esterification reaction, ispreferably 2 to 20 mol %, more preferably 2 to 10 mol %, further morepreferably 3 to 7 mol %, and most preferably 3 to 5 mol %.

By making the reaction rate 2 mol % or more, the tendency of thethickness loss of a non-exposed portion can be controlled. On the otherhand, by making the reaction rate 20 mol % or less, the tendency of thepermeability decrease for i-line radiation can be controlled anddecrease of sensitivity can be controlled, without impairing variouscharacteristics. Also, the fall of the perpendicularity of form can becontrolled. As the (A) component, one kind or a mixture of two or morekinds thereof can be used.

(B) Organic Solvent

-Propylene Glycol Alkyl Ether Acetate

By using propylene glycol alkyl ether acetate as the (B) component,development velocity can be increased. If the (B) component is used, thedissolution rate can be increased, without causing thickness loss of thenon-exposed part by development. Furthermore, development velocity canbe increased, maintaining the effect by the (A) component, i.e., thegood sensitivity and perpendicularity of resist pattern form.

Examples of propylene glycol alkyl ether acetate include propyleneglycol methyl ether acetate, propylene glycol ethyl ether acetate,propylene glycol propyl ether acetate, and the like.

Particularly from the viewpoint of an effect and availability, etc.,propylene glycol ethyl ether acetates are preferable. Propylene glycolalkyl ether acetates can be used as one kind or as mixture of two ormore kinds thereof.

-Mixture Solvent

The (B) component can comprise propylene glycol alkyl ether acetate 100%by weight, and it can also be blended with solvents other than propyleneglycol alkyl ether acetate. By blending solvents other than propyleneglycol alkyl ether acetate, good characteristics which are not acquiredby propylene glycol alkyl ether acetate, may further be given.

When making a mixed solvent, it is desirable to make the blending amountof propylene glycol alkyl ether acetate to 50 to 90% by weight, and moredesirably 70 to 90% by weight.

Within this range, the effect by propylene glycol alkyl ether acetate isfully acquired.

Other solvents to be mixed can be one kind or a mixture of two or morekinds thereof. Although they are not especially limited, as long as theycan be used for a resist composition, it is desirable to blend ethyllactate, for example for improvement of heat resistance. Ethyl lactatecan raise the heat resistance of the positive photoresist composition ofthe present invention, without greatly impairing the improvement effectof the development velocity of propylene glycol alkyl ether acetate, andis excellent.

Examples of other solvents which can be blended are ketones, such asacetone, methyl ethyl ketone, cyclohexanone, methyl isoamylketone,2-heptanone; polyhydric alcohols and the derivatives thereof (except forpropylene glycol mono-acetate derivatives, propylene glycol alkylether-acetate), such as ethylene glycol, propylene glycol, diethyleneglycol, ethylene glycol mono-acetate, propylene glycol mono-acetate,diethylene glycol mono-acetate, or mono-methyl ether, mono-ethyl ether,mono-propyl ether, mono-butyl ether, or mono-phenyl ether thereof; ringtype ethers, such as dioxane; and esters, such as methyl acetate, ethylacetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methoxy methylpropionate, and ethoxy ethyl propionate.

These may be used independently, or two or more of them may be mixed andused.

Although the amount of the (B) components used is not limitted, it isdesirable that solid content concentration in a positive photoresistcomposition account for the range of from 30% by weight to 65% byweight.

Other Components Which can be Blended

The positive photoresist of the present invention can further comprise,if necessary, plasticizers, such as an alkali soluble acrylate resin, anadhesion improver for increasing adhesion with a substrate, asensitizer, a high boiling point organic solvent, an acid generatingagent, or various addition components commonly used in the technicalfield concerned may be further blended with the positive photoresistcomposition of the present invention.

-Alkali Soluble Acrylate Resin

The positive photoresist composition of the present invention maycomprise an alkali soluble acrylate resin (hereinafter referred to as“(C) component”), as a plasticizer, in order to raise anti-platingproperty, such as preventing generation of cracks, in the use of fominga thick film resist layer, and plating is applied.

As the component (C), materials that are generally blended with thepositive photoresist composition as a plasticizer can be used.

As the component (C), those that contain 30 to 90% by weight of aconstitutional unit derived from a polymerizable compound which has anether linkage and 50 to 2% by weight of constitutional unit derived froma polymerizable compound which has a carboxyl group.

Examples of a polymerizable compound which has an ether linkage compriseradical polymerizable compounds, such as (meth)acrylic acid derivativeshaving an ether linkage and an ester linkage, such as 2-methoxy ethyl(meth)acrylate, methoxy triethylene glycol (meth)acrylate, 3-mehtoxybutyl (meth)acrylate, an ethyl carbitol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, methoxy polypropylene glycol(meth)acrylate, tetra-hydrofurfuril (meth)acrylate. Preferably, they are2-methoxyethyl acrylate and methoxy triethylene glycol acrylate.

These compounds can be used independently or in combination of two ormore of them.

Examples of polymerizable compound which has a carboxyl group compriseradical polymerizable compounds, such as monocarboxylic acid, such asacrylic acid, methacrylic acid, and crotonic acid; dicarboxylic acid,such as maleic acid, fumaric acid, and itaconic acid; and methacrylicacid derivative which has a carboxyl group and ester bonds, such as2-methacryloyloxy ethyl succinic acid, 2-methacryloyloxy ethyl maleate,2-methacryloyl ethyl phthalic acid, and 2-methacryloyloxy ethylhexahydro phthalic acid. Acrylic acid and methacrylic acid arepreferable.

These compounds are used independently or two or more of them can beused in combination.

The content of a polymerizable compound which has an ether linkage inthe (C) component preferably has 30 to 90% by weight, more preferably 40to 80% by weight. By making the content 90% by weight or less, atendency of generation of BENARD CELLS (a pentagon to heptagon networkpattern which has the heterogeneity produced on the coated film surfacedue to gravity or a surface tension slope) at the time of prebaking dueto deterioration of the compatibility over the solution of the (A)component which makes it difficult to obtain a uniform resist film, canbe controlled. By making the content 30% by weight or more, the crackgeneration can be controlled in the use of forming a thick resist filmresist layer and applying plating.

The content of a polymerizable compound which has a carboxyl group inthe (C) component is preferably 2 to 50% by weight, and more preferably5 to 40% by weight. By making the content 2% by weight or more, thetendency that the alkali solubility of the positive photoresistcomposition of the present invention will decrease, and the tendencythat sufficient developability will not be obtained can be prevented.Moreover, by making the content 2% by weight or more, a tendency thatthe release property of the positive photoresist of the presentinvention decreases and some residue of the resist remains on asubstrate can be controlled. By making the content 50% by weight orless, the tendency that the remaining rate of the film after developmentdecreases and plating resistance decreases can be controlled.

The average molecular weight of the (C) component is preferably 10,000to 800,000, and more preferably 30,000 to 500,000. By making themolecular weight 10,000 or more, a tendency that a resist film cannotobtain sufficient hardness, and thus causes the blister of the profileat the time of plating, and generating of cracks can be controlled. Bymaking the molecular weight 800,000 or less, the tendency for thereleasability of a resist film to decrease can be controlled.

Furthermore in the (C) component, other radical polymerizable compoundscan be included as a monomer in order to properly control a physical andchemical property. The above-mentioned “other radical polymerizablecompounds” means radical polymerizable compounds other than theabove-mentioned polymerizable compound.

Examples of such other radical polymerizable compound includes alkyl(meth)acryl esters, such as methyl (meth)acrylate, ethyl (meth)acrylate,butyl (meth)acrylate; hydroxy alkyl (meth)acrylate, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxy propyl (meth)acrylate; aryl(meth)acrylate, such as phenyl (meth)acyrlate, benzyl (meth)acrylate;dicarboxylic acid diesters, such as diethyl maleate, dibutyl fumarate;vinyl group containing aromatic compounds, such as styrene and α-methylstyrene; vinyl group containing aliphatic compound, such as vinylacetate; conjugation diolefin, such as butadiene and isoprene; nitrilegroup containing polymerizable compound, such as acrylonitrile andmethacrylonitrile; chlorine containing polymerizable compounds, such asvinyl chloride and vinylidene chloride; amide bond containingpolymerizable compounds, such as acrylamide and methacrylamide, etc.

These compounds can be used independently or two or more of them can beused in combination. Among these, n-butyl acrylate, benzyl methacrylate,methyl methacrylate, and the like are especially desirable.

In the (C) component, other radical polymerizable compounds account forpreferably 50% by weight or less, and more preferably, 40% by weight orless.

Examples of the polymerization solvent used for synthesis of the (C)component are alcohols, such as ethanol and diethylene glycol; ethyleneglycol monomethyl ether; alkyl ethers of polyhydric alcohols, such asdiethylene glycol monomethyl ether and diethylene glycol ethyl methylether; alkyl ether acetates of polyhydric alcohols, such as ethyleneglycol ethyl ether acetate, propylene glycol methyl ether acetate;aromatic hydrocarbon, such as toluene, xylene; ketones, such as acetoneand methyl isobutyl ketone; esters, such as ethyl acetate and butylacetate. Among these, especially desirable are the alkyl ether of apolyhydric alcohol and the alkyl ether acetate of a polyhydric alcohol.

As the polymerization catalyst used for synthesis of the (C) component,the usual radical polymerization initiator can be used, and examplesthereof includes azo compounds, such as 2,2′-azobis isobutyronitrile,and an organic peroxide, such as benzoyl peroxide and di-tert-butylperoxide, and the like.

In the positive photoresist composition of the present invention, theblending amount of the (C) component account for 20% by weight or less,and more preferably 10% by weight or less based on the (A) component. Bymaking the blending amount in this range, the hardness of the resistfilm formed will become sufficient, blistering etc., becomes unlikely tooccur, a clear profile is obtained, and resolution improves.

In addition, although the (C) component is not indispensable, and it isnot necessary to blend, when it is blended, more than 3% by weight basedon the (A) component is desirable.

-Adhesion Improver

Examples of an adhesion improver includes those disclosed in JapaneseUnexamined Patent Application, First Publication No. S62-262043,Japanese Unexamined Patent Application, First Publication No.H11-223937, etc.

For example, 6-methyl-8-hydroxyquinoline, 6-ethyl-8-hydroxyquinoline,5-methyl-8-hydroxyquinoline, 8-hydroxyquinoline, 8-acetyloxyquinoline,4-hydroxypteridine, 2,4-dihydroxypteridine, 4-hydroxypteridine-2-sulfonic acid, 2-ethyl-4-hydroxypteridine,2-methyl-4-hydroxypteridine, 1,10-phenanthroline,5,6-dimethyl-1,10-phenanthroline, 3,8-dimethyl-1,10-phenanthroline,3,8-dihydroxy-1,10-phenanthroline, 5-carboxy-1,10-phenanthroline,5,6-dihydroxy-1,10-phenanthroline, 1,10-phenanthroline-5-sulfonic acid,4,4′-dimethyl-2,2′-bipyridyl, 2,2′-bipyridyl,2,2′-bipyridyl-5-carboxylic acid, 5,5′-dichloro-2,2′-bipyridyl,3,3′-dihydroxy-2,2′-bipyridyl, 3,3′-dimercapto-2,2′-bipyridyl, etc. maybe mentioned.

The adhesive property over the substrate of a positive photoresistcomposition can be remarkably raised by blending the heterocyclicaromatic compound which has on a ring at least one selected from thebonds represented by the following general formula (d-3) and at leastone selected from the bonds represented by the following generalformulas (d-1) and (d-2).

wherein R34 represents hydrogen atom or an alkyl group having 1 to 3carbon atoms.

wherein R³⁵ represents hydroxyl group or an alkyl group of a linear orbranched chain with 1 to 5 carbon atoms which have a hydroxyl groupsubstituent.

The above-mentioned heterocyclic compound includes compounds indicatedin “organic compound constitutional formula index” (issued by MaruzenCo., Ltd., on Dec. 20, 1977) pp. 362-401, such as for example, thosewhich have a 5 member ring frame with one nitrogen atom, such as anindole compound, an indoline compound and an indigo compound; thosewhich have 6 member ring frame with one nitrogen atom, such as pyridinecompound, quinoline compound, hydroquinoline compound, isoquinolinecompound, acridine compound, a benzoquinoline compound, naphthoquinolinecompound, phenanthroline compound; those which have 5 member ring framewith two nitrogen atoms, such as pyrazole compound, imidazole compound,imidazoline compound, and benzoimidazole compound; those which have 6member ring frame with two nitrogen atoms, such as diazine compound,hydropyridine compound, benzodiazine compound, and dibenzodiazinecompound; those which have 5 member ring frame with three nitrogenatoms, such as triazole compound, benzotriazole compound; those whichhave 6 member ring frame with three nitrogen atoms, such as triazinecompound; those which have 5 member ring frame with 4 nitrogen atoms,such as tetrazole and pentetrazol; those which have 6 member ring framewith 4 nitrogen atoms, such as 1,2,4,5-tetrazine. In addition to these,purine compound, pteridine compound, alloxazine compound, 2H-pyrrole,etc., can be used.

Among these compounds, the compound represented by the following generalformula (d-4) is desirable in that it provides a positive photoresistcomposition which controls generation of scums and is excellent in theadhesive property over a substrate. Especially, 2-(2-hydroxy ethyl)pyridine is desirable.

wherein k represents an integer of 1 to 3, and R³⁵ represents the samemeaning as the above.

The addition amount of an adhesion improver is 0.1 to 1.0% by weight,more preferably 0.2 to 0.7% by weight based on the amount of sum totalsof the above (A) component and the above (C) component. By making theamount 0.1% by weight or more, the adhesive improvement effect over thesubstrate of a positive photoresist composition can fully be acquired.By making the amount 1.0% by weight or less, the decrease inresolvability and the tendency to generate scums on the substrate afterdevelopment can be controlled.

-Sensitizer

According to the present invention, a sensitizer can be blended ifnecessary. As a sensitizer which can be used by the present invention,there is no restriction in particular. Sensitizers usually used in apositive photoresist composition can be chosen arbitrarily.For example, the phenolic compound represented by the following generalformula (e-1) can be used.

wherein R⁴¹ to R⁴⁸ each represents, independently, a hydrogen atom, ahalogen atom, an alkyl group of 1 to 6 carbon atoms, an alkoxyl group of1 to 6 carbon atoms, or a cycloalkyl group; R⁵⁰ and R⁵¹ each represents,independently, a hydrogen atom, or an alkyl group of 1 to 6 carbon atomsrespectively; R⁴⁹ can be either a hydrogen atom or an alkyl group of 1to 6 carbon atoms, and in such cases, Q is either a hydrogen atom, analkyl group of 1 to 6 carbon atoms, or residue represented by a chemicalformula (e-2) shown below:

wherein, R⁵² and R⁵³ each represents, independently, a hydrogen atom, ahalogen atom, an alkyl group of 1 to 6 carbon atoms, an alkoxyl group of1 to 6 carbon atoms, or a cycloalkyl group; t represents an integer from1 to 3; or Q can be bonded to R⁴⁹, and in such cases, Q and R⁴⁹,together with the carbon atom between R⁴⁹ and Q form a cycloalkyl groupof 3 to 6 carbon atoms; w and s represent an integer of 1 to 3; urepresents an integer of 0 to 3; although when w, s or u is 3, then R⁴³,R⁴⁶, or R⁴⁸ respectively do not exist; and v represents an integer of 0to 3.Examples of the phenolic compound represented by the above generalformula (e-1) includebis(4-hydroxy-2,3,5-trimethylphenyl)-2-hydroxyphenylmethane,1,4-bis[1-(3,5-dimethyl-4-hydroxyphenyl)isopropyl]benzene,2,4-bis(3,5-dimethyl-4-hydroxyphenylmethyl)-6-methylphenol,bis(4-hydroxy-3,5-dimethylphenyl)-2-hydroxyphenylmethane,bis(4-hydroxy-2,5-dimethylphenyl)-2-hydroxyphenylmethane,bis(4-hydroxy-3,5-dimethylphenyl)-3,4-dihydroxyphnylmethane,1-[1-(4-hydroxyphenyl)isopropyl]-4-[1,1-bis(4-hydroxyphenyl)ethyl]benzene,1-[1-(3-methl-4-hydroxyphenyl)isopropyl]-4-[1,1-bis(3-methyl-4-hydroxyphenyl)ethyl]benzene, 2,6-bis[1-(2,4-dihydroxyphenyl)isopropyl]-4-methylphenol,4,6-bis[1-(4-hydroxyphenyl)isopropyl]resorcin,4,6-bis(3,5-dimethoxy-4-hydroxyphenylmethyl)pyrogallol,4,6-bis(3,5-dimethyl-4-hydroxyphenylmethyl)pyrogallol,2,6-bis(3-methyl-4,6-dihydroxyphenymethyl)-4-methyl phenol,2,6-bis(2,3,4-trihydroxyphenylmethyl)-4-methyl phenol,1,1-bis(4-hydroxyphenyl)cyclohexane etc. may be mentioned.

In addition to these,6-hydroxy-4a-(2,4-dihydroxyphenyl)-9-1′-spirocyclohexyl-1,2,3,4,4a,9a-hexahydroxanthene,6-hydroxy-5-methyl-4a-(2,4-dihydroxy-3-methylphenyl)-9-1′-spirocyclohexyl-1,2,3,4,4a,9a-hexahydroxanthene,and the like can be used.

These sensitizers can be used independently, or two or more of them canbe mixed and used. Among these, a combination of1-[1-(4-hydroxyphenyl)isopropyl]-4-[1,1-bis(4-hydroxyphenyl)ethyl]benzeneand bis(4-hydroxy-2,3,5-trimethylphenyl)-2-hydroxyphenylmethane isespecially superior in increasing sensitivity and the perpendicularityof a space pattern.

As a sensitizer, the phenolic compound represented by the followinggeneral formula (e-3) can be used.

In the general formula (e-3), R⁶¹ to R⁶³ each independently represents alower alkyl group (which may be linear or branched, and has preferably 1to 5 carbon atoms, more preferably 1 to 3 carbon atoms), cycloalkylgroup (preferably of 5 to 7 carbon atoms) or a lower alkoxy group (whichmay be linear or branched, and has preferably 1 to 5 carbon atoms, morepreferably 1 to 3 carbon atoms) independently among a general formula(e-3). q and r represent an integer from 1 to 3, preferably 1 to 2. l,o, and p represent an integer of 0, or 1 to 3.

More specifically, as a phenolic compound represented by the generalformula (e-3), the compounds represented by the following chemicalformula (e-4) to (e-8) are mentioned.

As a sensitizer, the phenolic compound represented by the followinggeneral formula (e-9) can also be used.

In the general formula (e-9), R⁷¹ to R⁷⁹ each independently represents ahydrogen atom, an alkyl group, a halogen atom, or a hydroxyl group. Atleast one of them is a hydroxyl group, and preferably at least 1 of R⁷¹to R⁷⁴ and at least 1 of R⁷⁵ to R⁷⁹ are hydroxyl group. Any alkyl groupin R⁷¹ to R⁷⁹ may be linear or branched, and has preferably 1 to 5carbon atoms, more preferably 1 to 3 carbon atoms.

R⁸⁰ to R⁸⁵ each independently represents a hydrogen atom, an alkylgroup, an alkenyl group, a cycloalkyl group, or an aryl group. Any alkylgroup in R⁸⁰ to R⁸⁵, may be linear or branched, and has preferably 1 to5 carbon atoms. As an alkenyl group, an alkenyl group of 1 to 4 carbonatoms is desirable.

More specifically, as a phenolic compound represented by a generalformula (e-9), the compounds represented by the following generalformula (e-10) may be mentioned.

wherein R⁸⁶ and R⁸⁷ each independently represents an alkyl group. Thealkyl groups may be linear or branched, and have preferably 1 to 5carbon atoms, more preferably 1 to 3 carbon atoms. f and g represents aninteger of 1 to 3, preferably 1 or 2. j and z represents an integer of0, or 1 to 3.

More specifically, as a phenolic compound represented by a generalformula (e-9), the compounds represented by the following formula (e-11)or (e-12) may be mentioned.

The blending amount of the sensitizer is preferably 1 to 30% by weightand more preferably 3 to 20% by weight, based on the above (A)component.

-High Boiling Point Organic Solvent

Furthermore, in the present invention, by adding an optional organicsolvent selected from a group consisting of high boiling point organicsolvents with a boiling points of 200 to 350° C., the bulk effect of theresist film, namely bias within the film density, can be reduced,meaning that even in those cases when the positive photoresistcomposition is used to form a thick resist film on the surface of asubstrate with level differences, a resist pattern with excellentperpendicularity can still be formed. Furthermore, a favourable resistpattern can be formed regardless of the conditions (heating time,heating devices and the like) for the prebake treatment and the PEB(post exposure heating) treatment.

Examples of the above high boiling point organic solvents include benzylacetate, isoamyl salicylate, methyl salicylate, benzyl salicylate,diethyl phthalate, dibutyl phthalate, dimethyl phthalate,γ-butyrolactone, ethyl benzoate, butyl benzoate, propyl benzoate, benzylbenzoate, ethylene glycol mono-phenyl ether, ethylene glycol mono-hexylether, 1,3-octylene glycol, diethylene glycol, diethylene glycoldiacetate, diethylene glycol dibutyl ether, diethylene glycol monoethylether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, dipropyleneglycol, dipropylene glycol mono butyl ether, triethylene glycol,triethylene glycol di-2-ethyl butylate, triethylene glycol dimethylether, triethylene glycol monoethyl ether, triethylene glycol monomethylether, tripropylene glycol, tripropylene glycol monomethyl ether,2-ethyl hexanoic acid, caprylic acid, caproic acid, catechol,octylphenol, and N-methyl pyrrolidone. These organic solvents may beused singularly, or in combination of two or more different solvents. Ofthe above solvents, those with a boiling point within the range from 250to 350° C. are preferred, and benzil salicylate is particularlydesirable.

The quantity added of the high boiling point organic solvent istypically within a range from 3 to 15% by weight, and preferably from 6to 12% by weight based on the combined quantity of the component (A),and if added, the above sensitizer. If the quantity is 3% by weight ormore, then the above effect can be sufficient, whereas, if the quantityis 15% by weight or less, then a tendency is controlled that the uppersections of the space pattern to expand, causing an undesirabledeterioration in the perpendicularity of the cross sectional shape.

Preparation Method of the Positive Photoresist Composition

The positive photoresist composition of the present invention isprepared by dissolving the above (A) component and the variouscomponents added if needed in the (B) component, and it is used in theform of a solution. Preparation of a positive photoresist compositionaccording to the present invention may be conducted simply by mixing andstirring together each of the components described above using normalmethods, or if necessary, by dispersion and mixing using a dispersiondevice such as a dissolver, a homogenizer or three roll mill.Furthermore, following mixing of the components, the composition mayalso be filtered using a mesh or a membrane filter or the like.

[Resist Pattern Formation Method]

A description follows of a preferred example of a method of forming aresist pattern according to the present invention.

First, the above positive photoresist composition is applied to thesurface formed from a material such as Au, Si, and Cu, or the like usinga spinner or the like, and is then dried to form a photosensitive layer.This photosensitive layer is then exposed through a desired maskpattern, using a light source, such as a high pressure mercury lamp, anultra high pressure mercury lamp, or a low pressure mercury lamp. Whererequired, a PEB (post exposure baking) treatment is then performed, andthe exposed portions of the film are then dissolved and removed byimmersing the substrate in a developing liquid, for example, an alkalineaqueous solution such as a 1 to 10% by weight aqueous solution oftetramethylammonium hydroxide (TMAH), thus forming an image which isfaithful to the mask pattern.

In those cases where a resist pattern with a high aspect ratio with awidth of no more than 0.8 μm is formed under thick film conditions of atleast 3 μm, and particularly from 6 to 8 μm, a conventional patternformation method using an acid cross linking material can also be usedif required.

Examples of such conventional methods include resist pattern formationmethods comprising the steps of: forming a film of an acid cross linkingmaterial, which causes a cross linking reaction under the action ofacid, across the entire surface of the substrate on which the resistpattern has been drawn, conducting heat treatment so that the action ofacid diffusing from the resist pattern surface causes cross linking ofthe acid cross linking material in those portions contacting the resistpattern, and using a developing liquid to remove the acid cross linkingmaterial from those areas that have not undergone cross linking, therebyforming a resist pattern with a narrower space width than that of theresist pattern prior to formation of the acid cross linking materialfilm. Other examples include resist pattern formation methods comprisingthe steps of: forming a film of an acid cross linking material, whichcauses a cross linking reaction under the action of acid, across theentire surface of the substrate on which the resist pattern has beendrawn, generating acid at the surface of, or inside, the resist patternby conducting either selective exposure or complete exposure of thesubstrate surface using ultraviolet radiation, conducting heat treatmentso that the action of acid diffusing from the resist pattern surfacecauses cross linking of the acid cross linking material in thoseportions contacting the resist pattern, and using a developing liquid toremove the acid cross linking material from those areas that have notundergone cross linking, thereby forming a resist pattern with anarrower space width than that of the resist pattern prior to formationof the acid cross linking material film.

There are no particular restrictions on the acid cross linking materialand the developing liquid used, and suitable examples include thematerials disclosed in Japanese Unexamined Patent Application, FirstPublication No. Hei 11-204399.

In the present invention the development velocity can be increased byusing the (B) component in the positive photoresist composition and theresist pattern formation method. Moreover, the thickness loss bydevelopment can be prevented. Good sensitivity is obtained by using the(A) component.

Moreover, a surfactant can also be blended with the composition of thepresent invention if needed in order to raise coating performance,anti-foaming property, leveling property, etc. Surfactants, such asfluorine based surfactants such as for example BM-1000, BM-1100 (tradename, manufactured by BM Chemie), MEGAFAC F142D, MEGAFAC F172, MEGAFACF173, MEGAFAC F183 (manufactured by Dainippon Ink & Chemicals, Inc.),FLUORAD FC-135, FLUORAD FC-170C, FLUORAD FC-430, FLUOLAD FC-431(manufacrured by Sumitomo 3M Co., Ltd.), SURFRON S-112, SURFRON S-113,SURFRON S-131, SURFRON S-141, SURFRONS-145 (trade name, manufactured byAsahi Glass Co., Ltd.), SH-28PA, SH-190, SH-193, SZ-6032, SF-8428 (tradename, manufactured by Dow Corning Toray Silicone Co.,Ltd.), etc., can beused in the present invention. The amount of these surfactants used ispreferably 1% by weight or less, based on the total resist solidcomponent.

EXAMPLES Synthetic Example

50 g of a polycondensation product (1) (Mw=4000, dispersity (Mw/Mn)=5.0,synthesized by a dehydration condensation reaction of m-cresol, p-cresol(molar ratio=36:64) and formalin, and 5 g of1,2-naphthoquinonediazide-5-sulfonyl chloride were placed in a 1 liter3-necked flask equipped with a thermometer, a stirrer, and a droppingfunnel. 150 g of 2-heptanone was then added to dissolve the mixture, and3.8 g of triethylamine was added from the dropping funnel. The reactionmixture was then stirred for 1 hour at room temperature to allow thereaction to proceed.

Subsequently, 5.8 g of a 35% aqueous hydrochloric acid solution wasadded, and futher stirring was continued at room temperature for 30minutes. Next, to this reaction product solution, 150 g of water wasadded and agitated, thereafter, superfluous hydrochloric acid wasremoved by standing the reaction product solution and removing theseparated aqueous layer. By the above operation, 2-heptanone solution ofthe photosensitive novolak resin (2) wich is formed by replacing 4.5 mol% of hydrogen atoms within those of all phenolic hydroxyl groups werereplaced by 1,2-naphthoquinonediazide-5-sulfonyl group.

Example 1

The above 2-heptanone solution of the photosensitive novolak resin (2)was concentrated, and operation of adding propylene glycol methyl etheracetate thereto and concentrating thereof was repeated 3 times, and 55%by weight solution of novolak resin (2) in propylene glycol methyl etheracetate was obtained.

Subsequently, propylene glycol methyl ether acetate was added so thatthe concentration of photosensitive novolak resin (2) might become 42%by weight, to 100 weight part of the photosensitive novolak resin (2)(182 weight part of the 55% by weight solution of propylene glycolmethyl ether acetate), and a positive photoresist composition whichcontains propylene glycol methyl ether acetate as the solvent wasprepared.

Example 2

By adding propylene glycol methyl ether acetate and ethyl lactate sothat the concentration of photosensitive novolak resin (2) may become42% by weight, to 100 weight part of the photosensitive novolak resin(2) (182 weight part of the 55% by weight solution of propylene glycolmethyl ether acetate), and a positive photoresist composition whichcontains propylene glycol methyl ether acetate and ethyl lactate (weightratio=70/30) as the solvent was prepared.

Comparative Example 1

The above 2-heptanone solution of photosensitive novolak resin (2) wasconcentrated, and operation of adding ethyl lactate thereto andconcentrating thereof was repeated 3 times, and 55% by weight solutionof photosensitive novolak resin (2) in ethyl lactate was obtained.

By adding ethyl lactate so that photosensitive novolak resin (2)concentration may become 42% by weight solution of photosensitivenovolak resin (2) (182 weight part of the 55% by weight solution ofethyl lactate), and a positive photoresist composition which containethyl lactate as the solvent was prepared.

Comparative Example 2

By concentrating 2-heptanone solution of photosensitive novolak resin(2), a 55% by weight solution of 2-heptanone was obtained.

By adding 2-heptanone so that novolak resin (2) concentration may become42% by weight solution of photosensitive novolak resin (2) (182 weightpart of the 55% by weight solutions of 2-heptanone), and a positivephotoresist composition which contain 2-heptanone as the solvent wasprepared.

Comparative Example 3

Component (A-1): Polycondensation material (1) 100 weight part

Component (A-2): A photosensitizer formed by replacing two mols of thehydrogen atom within those of all phenolic hydroxyl groups of1-[1-(4-hydroxyphenyl)isopropyl]-4-[1,1-bis(4-hydroxyphenyl)ethyl]benzeneby 1,2-naphthoquinonediazide-5-sulfonyl group 18 weight parts

By adding propylene glycol methyl ether acetate so that sum totalconcentration of each of the above components may become 42% by weight,a positive photoresist composition which contained propylene glycolmethyl ether acetate as the solvent was prepared.

The positive photoresist compositions of the examples and comparativeexamples prepared by the above method were estimated, and the resultsare shown in Table 1.

(Developability Evaluation)

The samples were applied with a spinner on an Si substrate which hadbeen treated by hexamethyl disilazane (HMDS), and was then dried on ahotplate at 100° C. for 90 seconds, thus forming a resist film with afilm thickness of 5.0 μm.

Subsequently, the film was exposed so that a line:space might befinished 1:1 on this film using a reduction projection exposureapparatus NSR-2005i10D (manufactured by NIKON CORP., NA=0.50) through amask with which a predetermined shading pattern (5 μm line & space) wasdrawn.

Subsequently, as development operation, a 23° C. 2.38% by weighttetra-methylammonium hydroxide (TMAH) aqueous solution was applied on asubstrate, and after 30 seconds contact, was removed by rotating thespinner. This processing of rotation removement was repeated until anobservation after a rotation removement exhibited a pattern wherein thespace portion was removed and the line:space becomes 1:1.

The developability was assessed by the number of the rotationremovement. Two or less of the number was ranked as A; 3 of the numberwas ranked as B; 4 of the number was ranked as C; 5 or more of thenumber was ranked as D.

(Sensitivity Evaluation)

Application, exposure, and development were performed in the same way asthe above Developability evaluation, and the light exposure (E) requiredto form a 5 μm was recorded. The sensitivity was estimated as A, whenE≦500 ms; and as C, when 500 ms<E.

(Resist Form Evaluation)

Exposure and development were performed in the same way as the aboveDevelopability evaluation, and the angle (R) between the side wall of a5 μm line and a substrate was measured. The resist form was evaluated asA, when 85°<R; as B, when 70°<R≦85°; and as C, when R≦70°.

(Heat Resistance Evaluation)

The samples were applied with a spinner on a substrate which had beentreated by HMDS, and was then dried on a hotplate at 100° C. for 90seconds, thus forming a resist film with a film thickness of 3.0 μm.

Subsequently, the film was exposed, through a mask with a maskdimensions of 5 μm (for forming a 5 μm line pattern), using a reductionprojection exposure apparatus NSR-2005i10D (manufactured by NIKON CORP.,NA=0.50), so that a 5 μm line pattern was formed, and the film was thensubjected to PEB treatment at 100° C. for 90 seconds.

As the developing operation, a 2.38% by weight aqueous solution oftetramethylammonium hydroxide (TMAH) at 23° C. was then applied to thesubstrate surface, and after 60 seconds contact, was removed by rotatingthe spinner. The film was then washed with water for 30 seconds anddried, and the resulting substrate with 5 μm line pattern thereon wassubjected to heat treatment on a hotplate at 120° C. for 600 seconds.

The cross sectional shape of the 5 μm line pattern was then viewed via aSEM (scanning electron microscope) photograph, and the angle between thesubstrate interface and a straight line connecting the point ofintersection (point (a) in FIG. 1) between the substrate interface andthe side wall of the resist pattern, and the corner (point (b) inFIG. 1) at the top of the resist pattern was termed θ. Patterns forwhich θ>80° were recorded as “A”, patterns for which 80°≧θ and in whichthe corner still existed at the top of the resist pattern were recordedas “B”, and patterns in which the corner no longer existed at the top ofthe resist pattern, making measurement impossible, were recorded as “C”.TABLE 1 Developability Sensitivity Resist form Heat resistanceevaluation evaluation evaluation evaluation Example 1 A A A B Example 2B A A A Comp. Ex. 1 C A A A Comp. Ex. 2 D A B A Comp. Ex. 3 A C C C

From the result shown in Table 1, the positive photoresist compositionof the present invention apparently provide good results in bothdevelopment velocity and sensitivity, and improves development velocitywhile maintaining the characteristics of the (A) component. Moreover, inresist form evaluation, the phenomenon of the head of a pattern becominground was not observed, but a high perpendicularity was obtained.Furthermore, heat-resistant evaluation increased in Exmaple 2, wherein amixed solvent of propylene glycol methyl ether acetate and ethyl lactatewas used.

In Example 2, although the developability evaluation of the positivephotoresist composition decreased slightly, it was satisfactory forpractical use.

1. A positive photoresist composition formed by dissolving (A)photosensitive novolak resin comprising an alkali soluble novolak resinwherein some hydrogen atoms within those of all phenolic hydroxyl groupsof the alkali soluble novolak resin are substituted by1,2-naphthoquinone diazide sulfonyl groups, in (B) an organic solventcontaining a propylene glycol alkyl ether acetate.
 2. The positivephotoresist composition according to claim 1, wherein the alkali solublenovolak resin has the following characteristics (1)-(3): (1) apolystyrene equivalent weight average molecular weight of 1000 to 30000,(2) a degree of dispersion of 25 or less, and (3) a rate of solution toa 2.38% by weight TMAH (tetra-methyl ammonium hydroxide) aqueoussolution at 23° C. is 10 to 1000 Å/s, and wherein the proportion ofsubstitution of the hydrogen atoms within those of all phenolic hydroxylgroups of the alkali soluble novolak resin by 1,2-naphthoquinone diazidesulfonyl group is 2 to 20 mol %.
 3. The positive photoresist compositionaccording to claim 1, wherein the propylene glycol alkyl ether acetateis propylene glycol methyl ether acetate.
 4. The positive photoresistcomposition according to claim 1, wherein the organic solvent (B)contains a solvent other than the propylene glycol alkyl ether acetate.5. The positive photoresist composition according to claim 4, whereinthe rate of the propylene glycol alkyl ether acetate in the organicsolvent (B) is 50 to 90 weight %.
 6. The positive photoresistcomposition according to claim 4, wherein the solvent other than thepropylene glycol alkyl ether acetate is ethyl lactate.
 7. A resistpattern formation method comprising the steps of coating a positivephotoresist composition according any one of claims 1 to 6 on asubstrate, prebaking the coated film, selectively exposing the film, andsubsequently alkali developing the film.